Bayly and Harper begin with pre-war society, describing the imperial heyday of the 1930s, based on surprisingly fragile foundations, and the stirrings of nationalism and other discontents. (Strangely, Malaysia is covered in "Prologue Part II" and India and Burma in chapter one.) They also describe the Japanese penetration into Southeast Asia through informal and formal networks, through traders and tourists and spies. There isn't room for much background history here, however: those unfamiliar with the region should be able to follow Forgotten Armies, but some context would help.
Forgotten Armies describes the Japanese attack, the ignominious British defeats in Malaysia, Singapore, and Burma, and the slow Allied recovery and victorious return. It is not, however, a military history. The battles for Kohima and Imphal are described in just a few pages, and the sinking of the Prince of Wales and the Repulse in one; there are no low level accounts of battle; and there are only passing mentions of key technologies such as the Japanese use of tanks, the early successes of Hurricanes, or the withdrawal of the radar system from Rangoon.
Bayly and Harper do an excellent job covering the broader and arguably more important aspects of war: the "malaria, monsoon and morale" that were key on the Burmese front, the armies of labourers behind the lines, the reformation of recruitment and management in the Indian army, and so forth. They also cover the tensions between British, American, Chinese and local leaders, and between civilians and military; on the other side, the differing attitudes of Japanese leaders to nationalist movements and leaders, and the conflicts with, and within, the Burma Defence Army, the Indian National Army, and other organisations.
A myriad of details help to convey a picture of Malaysia and Burma under Japanese occupation, and of India mobilised for war: the Chinese community in Singapore, faced with massacres and a huge fine; the terrible situation of refugees along the India-Burma border and the plight of Anglo-Burmans under the Japanese; bourgeois Singaporeans fleeing to the new jungle settlements of Bahau and Endau; the Bengal famine; the importance of cloth in Burma; currency and counterfeiting; the poor health of Indian labourers on the Assam front; and much more.
All this encompasses a fascinating array of people. The obvious figures include Allied commanders and officials like Wingate and Mountbatten and Dorman-Smith and Stilwell, nationalist leaders like Aung San and Subhas Chandra Bose and Ba Maw, and more distant figures such as Gandhi, Nehru and Churchill. There are also a host of lesser known figures: Japanese colonel Suzuki Keiji, who organised pre-war intelligence networks across Southeast Asia; Tan Kah Kee, unofficial leader of the Malay Chinese; the anthropologist Edmund Leach, carrying out fieldwork in the Burmese hills; the mysterious Lai Teck, the Malaysian Communist Party leader who was also a Japanese agent; and many more.
Bayly and Harper draw on a broad range of sources, notably a large number of memoirs and diaries, starting with Jean Cocteau's comments on British Southeast Asia during a round-the-world trip in 1936. One big limitation of Forgotten Armies, however, is its dependence on sources in English: the only Japanese perspective given prominence is that of an interpreter "Mr Nakane", known through a crude English diary.
The narrative stops abruptly with the Japanese surrender; it covers events after the Allied return in Burma but not in Malaysia. The explanation for this is that Bayly and Harper have a forthcoming book Forgotten Wars: Freedom and Revolution in Southeast Asia, which will cover the post-war conflicts and the achievement of independence by Malaysia and Burma. I'm looking forward to it.